50 national geographic • july 2016
DNA prediction
10-20 facial spectra
are typically calculated.
Variance from
average face
GENOMIC ANCESTRY
27.4%
68.1%
22.8%
0%
0%
0%
50.5%
62.2%
25%
Degree of
consistency
0%
100%
59.6%
50%
79.2%
0.7%
17.9%
46.2%
51.9%
85.5%
Proportion
of DNA
0%
100%
0%
0%
0%
98.3%
SKIN COLOR
0%
5.7%
FRECKLES
9%
EYE COLOR
0%
HAIR COLOR
5.3%
4.3%
AFRICAN
NATIVE AMERICAN
OCEANIAN
MIDDLE EASTERN
EAST ASIAN
CENTRAL ASIAN
EUROPEAN
NORTHWEST EUROPEAN
CENTRAL WEST EUROPEAN
DARK OLIVE
DARK
VERY FAIR
LIGHT OLIVE
FAIR
BROWN
BLACK
BLUE
HAZEL
GREEN
BLOND
BLACK
RED
BROWN
ZERO
SOME
MANY
FEW
Putting a Face to a Case
When a DNA sample found at a crime scene fails to match a sequence in any
database, law enforcement can now use a technology called DNA phenotyp-
ing to reverse engineer the face of its source, in this case the Lake Charles
killer. The technique converts genetic evidence into code that is passed
through complex mathematical algorithms to predict physical traits. Experts
emphasize that the resulting face is most helpful at ruling out people who
don’t match the profile rather than at identifying a particular person.
The evidence
Forensic specialists collect
biological evidence from
the crime scene and send it
to a DNA lab, where about
a million genetic markers
are scanned.
Predictive pipeline
By comparing the crime scene DNA with
the database, the algorithms can begin
to predict traits like ancestry, skin, hair, and
eye color. Each prediction narrows down
the possible physical characteristics of the
subject and begins to exclude unlikely traits.
The database
A database containing 3-D
facial scans and DNA for
thousands of people is
used to generate sophisti-
cated algorithms matching
DNA with physical traits.
JASON TREAT AND RYAN WILLIAMS, NGM STAFF
SOURCES: THOM SHAW (FORENSIC ART) AND STEVEN
ARMENTROUT, PARABON NANOLABS, INC.
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